Deep Dive into a SQL Query

Have you ever wondered what actually happens inside PostgreSQL when you run a SQL query?

Behind a simple SELECT statement lies a sophisticated pipeline involving parsing, semantic analysis, query rewriting, cost-based optimization, and a pull-based execution engine — built on decades of database research.

This book follows a query through every stage of that pipeline: lexical analysis and parsing, semantic validation against the system catalog, rule-based rewriting, cost-based plan optimization, and iterator-based execution. Along the way, you will see how PostgreSQL manages memory, organizes data on disk, coordinates concurrent access, and returns results to clients.